use absolutely-qualified namespaces in xlog macros
use absolutely-qualified namespaces in xlog macros

Summary: Macro definitions that may be used in C++ are generally required to use only absolutely-qualified namespaces, unless the intention is namespace-based customizations.

Reviewed By: simpkins

Differential Revision: D40244033

fbshipit-source-id: dbef164604ef0960898bd8ff160f854fc1ca06c8

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